A flow channel including bifurcations in midway is known, for example. In the flow channel, the upstream and downstream sides of the bifurcations extend substantially in the same direction, but the upstream and downstream sides of the bifurcations are shifted in position from each other in a direction perpendicular to the same direction.
For example, when a fluid flows from upstream to downstream in the above-described flow channel, the fluid may become uneven in the shifted direction from upstream to downstream.